During the last decade in particular, there has been a considerable increase in sales of flavoured tea. This is due partly to the attraction felt by the customer for non-traditional tea-based drinks such as soluble tea, iced tea, various liquid mixtures ready for consumption or carbonated drinks, which are on offer in various forms, in bottles, cans or cartons.
Most of these drinks are enriched with natural or synthetic flavours. Traditionally tea has been flavoured by adding certain essential oils, e.g. jasmine or rose essence, or spices such as cinnamon, cardamom or mint, or fruit flavours, e.g. strawberry, peach, banana or grape.
On the other hand, tea acquires its characteristic aroma during the various stages of maturing and packaging. Withering and curling of leaves, fermentation and drying are other operations which modify the original taste and flavour of tea and which, like the nature of the soil and climatic conditions of the place where the plant is cultivated, determine its aromatic characteristics.
Although systematic studies have not been made, experience has shown that prolonged storage of tea leaves after fermentation destroys the aroma, and hence there is a need for flavouring.
Usually flavouring is done simply by spraying the flavour in solution in an inert edible solvent on to the leaves, or by mixing the leaves with solid particles containing the flavouring, in which the case the technique of microencapsulation of the "fluidised bed" process is used. [See e.g. European patent application No. 70719 published on Jan. 26, 1983].
However, these methods have serious disadvantages. Firstly, the method of spraying a solution of flavouring is inefficient in that the dispersed flavouring tends to evaporate from the surface of the treated leaves in a relatively short time. On the other hand, the method using solid flavoured capsules is inconvenient in operation since it has been found that the particles tend to separate by gravity from the mass of leaves and accumulate at the bottom of the vessel in which they are stored or transported. In both cases, flavouring is non-uniform.